There are many applications where it would be desirable to attach a sensing device to a flexible and compliant structure, such as the human body for example, which is capable of undergoing dynamic and large deformations and strains. This feedback could be used for applications such as measuring strain or deformation for scientific or research purposes, to capture motion for use in movies or animation, or to use the structure as an input to some process, such as a human machine interface for example, just to name a few.
However, if the sensing device itself is relatively hard, inflexible, or non-compliant, or some combination of these, it may have an undesirable influence on the properties of the structure, restrict or alter the natural strain or deformation response of the flexible and compliant structure so it no longer accurately represents its natural strain or deformation response, or make it difficult to correlate the state of the sensing device and the state of the flexible and compliant structure, for example. To overcome this limitation, it is advantageous for the sensing device to be flexible, compliant and lightweight to minimize any impact on the structure being measured.
Flexible and compliant soft polymer thin films have application in unobtrusive sensing devices, to give an example. A sensing device however must typically also incorporate a substantially electrically conductive feature to provide a conductive pathway for electrical signals used in the sensing process. This can be achieved by creating a flexible and compliant film that is substantially electrically conductive by dispersing a sufficient percentage by volume conductive particles such as carbon powder into a polymer matrix such as silicone, for example. Robust sensing elements can be created using a combination of these electrically conductive films and electrically non-conductive films.
Flexible and compliant electrical components such as resistors and capacitors with deformation dependent properties can be made by laminating electrically non-conductive and electrically conductive layers. For example, a Dielectric Elastomer (DE) is a stackable flexible and compliant capacitor consisting of flexible and compliant dielectric that is substantially electrically non-conductive sandwiched between two flexible and compliant electrodes. A DE can be used as a flexible and compliant sensor by using electronic circuits to monitor one or more of properties such as capacitance, the resistance of the electrodes, and the conductivity of the dielectric, which are affected by stimuli such as the DE being stretched, for example.
A challenge with fabricating laminates of materials for sensing devices or for dielectric elastomer devices is that the dispersants used to provide conductivity in one layer of the laminate may contaminate dielectric layers. This contamination may lead to reduced dielectric effect or of the dielectric layers and diminish the operation of the sensors.
Another challenge is in fabricating laminates with layers as thin as possible. Challenges in fabricating laminates for devices with thin films often result in defects such as particulates, air bubbles, or areas of weak bonding. These may compromise the structural integrity of the device by creating a stress riser, a region of inhomogeneous strain, or promoting separation of the layers.
Other challenges lie in compounding the challenges above, such as in mitigating contamination as laminates with progressively thinner layers are fabricated.
It would therefore be of advantage to have a method of fabricating laminates for devices from flexible and compliant films which could address any or all of the above challenges, or at least provide the public with an alternative choice.
It would also be of advantage to have a laminate for a device from flexible and compliant films which could address any or all of the above challenges, or at least provide the public with an alternative choice.